1. Field of the Invention
The present invention relates to an image processing apparatus capable of carrying out a special processing on a document with a ground tint pattern.
2. Description of the Related Art
Due to improvements in image processing and image formation techniques, copying machines can produce elaborate copies of banknote that can hardly be distinguished from a real banknote. One approach is to provide an image processing apparatus with a function of determining whether an image read by a scanner is a special document, such as a banknote or a valuable security, and prohibiting illegal reproduction or transfer of such image data.
Japanese Patent Application Laid-open No. 2004-200897 discloses an image processing apparatus provided with a function of recognizing a special document. This image processing apparatus includes a ground-tint-pattern recognizing unit that recognizes a special document by comparing a ground tint pattern extracted from an image read from a document with a reference ground tint pattern. When the ground-tint-pattern recognizing unit recognizes that the document is a special document, the image processing apparatus prohibits the image from being printed, or performs a processing on the image by whitening the image, for example, or prohibits the image from being transferred outside, thereby preventing leakage of the image of the special document. Moreover, a user can freely change the reference ground tint pattern or change a determination standard.
However, the conventional technology is not capable of detecting an abnormality in the ground-tint-pattern recognizing unit. Therefore, when an abnormality occurs, a ground tint pattern cannot be checked. As a result, the image processing apparatus cannot be prevented from reading an image from a special document, and producing illegal reproductions of the image.